This invention relates generally to the generation and provision of refrigeration, and is particularly useful for providing refrigeration over a large temperature range and to very low temperatures.
Refrigeration is typically provided to a heat load by generating refrigeration and providing the refrigeration to a recirculating refrigeration fluid passing between the refrigeration generator and the heat load. This system works well when the heat load is to be cooled to a temperature not appreciably below atmospheric, such as an air conditioning system or a food freezing system. However, when it is desired to cool the heat load to a much colder temperature, such as to a cryogenic temperature at or below 200K, conventional refrigeration systems are inefficient and costly to operate.
Accordingly, it is an object of this invention to provide a refrigeration system which can efficiently provide refrigeration to a heat load especially at a cryogenic temperature.
The above and other objects, which will become apparent to those skilled in the art upon a reading of this disclosure, are attained by the present invention, which comprises in general the generation of refrigeration at a relatively higher level using a magnetic refrigeration system, and the generation of lower level refrigeration using a system other than a magnetic refrigeration system, to produce first a cooled refrigeration fluid at a temperature within the range of from 30 to 290K, preferably from 50 to 120K, and then a cold refrigeration fluid at a temperature within the range of from 2 to 270K, preferably from 4 to 100 k, which is used to provide the refrigeration to the heat load. More specifically, one aspect of the two step refrigeration system of this invention is:
A method for providing refrigeration to a heat load comprising:
(A) magnetizing a bed of magnetizable material, demagnetizing the magnetized bed material, cooling working fluid by bringing the working fluid into contact with the demagnetized bed material, and cooling heat transfer medium by indirect heat exchange with the cooled working fluid;
(B) warming the cooled heat transfer medium by indirect heat exchange with refrigeration fluid to produce cooled refrigeration fluid at a first temperature within the range of from 30 to 290K;
(C) providing refrigeration into the cooled refrigeration fluid to produce cold refrigeration fluid at a second temperature lower than said first temperature and within the range of from 2 to 270;
(D) warming the cold refrigeration fluid by passing refrigeration from the cold refrigeration fluid into a heat load.
Another aspect of the invention is:
Apparatus for providing refrigeration to a heat load comprising:
(A) a magnetic refrigerator having a bed of magnetizable material, means for magnetizing and demagnetizing the bed of magnetizable material, and containing working fluid for contact with the bed of magnetizable material;
(B) a heat transfer medium circuit comprising a heat transfer medium heat exchanger, means for passing heat transfer medium from the magnetic refrigerator to the heat transfer medium heat exchanger, and means for passing heat transfer medium from the heat transfer medium heat exchange to the magnetic refrigerator;
(C) means for passing refrigeration fluid to the heat transfer medium heat exchanger, and means for providing refrigeration into the refrigeration fluid downstream of the heat transfer medium heat exchanger; and
(D) a heat load and means for passing refrigeration from the refrigeration fluid into the heat load.
As used herein, the term xe2x80x9cindirect heat exchangexe2x80x9d means the bringing of fluids into heat exchange relation without any physical contact or intermixing of the fluids with each other.
As used herein, the term xe2x80x9cdirect heat exchangexe2x80x9d means the transfer of refrigeration through contact of cooling and heating entities.
As used herein, the term xe2x80x9cmagnetizexe2x80x9d means to induce magnetic properties to a substance by use of an externally applied electrical field.
As used herein, the term xe2x80x9cheat loadxe2x80x9d means an entity at a higher temperature capable of receiving refrigeration and thus being cooled to a lower temperature.